catgut

catgut or gut, cord made from the intestines of various animals (especially sheep and horses, but not cats). The membrane is chemically treated, and slender strands are woven together into cords of great strength, which are used for stringing musical instruments such as the violin and the harp. Roman strings, imported from Italy, are considered the best for musical instruments. Catgut is also used for stringing tennis rackets and for some surgical sutures.